Optical communication systems are known in which optical signals are modulated to carry data from a transmitter to a receiver over an optical link, such as an optical fiber. Various coding techniques, such as forward error correction (FEC), are known in which the transmitted data is encoded to include additional error correcting bits or syndromes. At the receiver, a decoder may be provided that decodes the encoded data and corrects errors that may have occurred during transmission based on the error correcting bits.
As data rates have increased, the number of bits to be decoded over a given period of time has also increased. Accordingly, many decoders have become increasingly complex and typically include a relatively high number of components, such as transistors or logic gates. Alternatively, a less complex iterative decoder may be provided that has fewer components. In such iterative decoders, data is decoded in a first iteration of the decoder, fed back to the input of the decoder, and decoded further by the decoder. This process may repeated, and, with each pass or iteration through the decoder, more errors are corrected. Preferably, however, the number of iterations performed by the decoder should be limited to a minimum in order to increase speed of the decoder.
Different optical links may require varying degrees of error correction. For example, certain fiber types may introduce less dispersion or other non-linear optical effects than others. Accordingly, depending on characteristics of the optical fiber and other system parameters, some optical communication systems may require more error correction than others. If such systems include an iterative decoder, the iterative decoder may perform fewer iterations if there are fewer errors to correct. On the other hand, if more errors are present, a higher number of iterations may be required.
Accordingly, there is a need to accurately identify an adequate number of iterations required to be performed by an iterative decoder to provide sufficient error correction.